The present invention relates generally to a receiver paper used in combination with a thermally transferable sheet, such as an ink ribbon, and on to which the dye from the thermally transferable sheet is transferred on application of heat.
A method employing a sublimable dye or a thermally fusible dye is used for developing the picture information inputted to a video apparatus onto a receiver paper, such as a printing paper sheet.
In this thermal transfer method, a thermally transferrable sheet (ink ribbon) having formed thereon a dye layer containing a sublimable dye or a thermally fusible dye, and a receiver paper (printing paper sheet), having formed thereon a reception layer for receiving the dye, are superimposed on one another, so that the dye layer will face the reception layer, and heat is applied by e.g., a thermal head in a dot pattern responsive to picture signals. This causes the dye in the dye layer to be sublimed or fused and transferred to the reception layer of the printing paper sheet to manifest the picture on the printing paper sheet.
This receiver paper is of a dual layer structure comprised of a sheet-like substrate and the reception layer formed thereon. This reception layer is a layer for receiving a picture of a dye transferred from the ink ribbon, for example, a picture of a sublimable disperse dye, and for maintaining the picture formed on reception, and is routinely formed of a resin exhibiting dyeing properties, such as polyester, polycarbonate or polyvinyl chloride.
For improving heat resistance, polyisocyanate, as a hardener, is sometimes added to the reception layer. Also, for improving transfer sensitivity and light-fastness, that is resistance to light, plasticizers are sometimes added to the reception layer. In addition, silicone oil, as a release agent, is sometimes added to the reception layer for improving peeling of the receiver paper from the dye layer surface.
On the other hand, the thermally transferrable sheet is routinely comprised of a substrate of, for example, polyester, and ink layers of respective colors, namely yellow, magenta, cyan and, if necessary, black, formed surface-sequentially thereon. In addition to the respective ink layers, a laminate layer may be provided, which is tranferred as a protective layer on the reception layer after forming the picture on the receiver paper. That is, the thermally transferrable sheet, carrying the laminated layer, can form a protective layer on the reception layer of the receiver paper.
If, in the above-described receiver paper, the transfer properties of the laminate layer are to be improved, it may be contemplated to decrease the amount of addition of a hardener, such as polyisocyanate, which is added to the reception layer, or to add a plasticizer to the reception layer to lower the glass transition temperature of the resin to soften the reception layer. However, in such case, the ink surface of the thermally transferrable sheet is fused to the reception layer of the receiver paper to detract from the quality of the formed picture or to cause running troubles. Also, the reception layer is softened in this case, so that, if plural receiver papers stacked together for storage under high temperature conditions, the so-called blocking, in which the reception layer 2 tends to be stuck to the back surface of the receiver paper, is likely to be produced.
On the other hand, if, in the above-described receiver paper, the running performance or resistance to blocking under high temperature conditions is to be improved, it may be contemplated to increase the amount of addition of the hardener, such as polyisocyanate, to harden the reception layer, or to increase the amount of addition of silicone oil to improve release properties between the thermally transferrable sheet and the receiver paper. However, in this case, the laminate layer of the receiver paper is worsened in transfer characteristics such that the laminate layer cannot be transferred or transferred only incompletely.
Thus, in the conventional receiver paper, there is a relation of trade-off between the transfer characteristics of the laminate layer on one hand and the running performance and resistance against blocking under high temperature conditions, such that the two requirements cannot be met simultaneously.
It is therefore an object of the present invention to provide a receiver paper onto which the laminate layer of the thermally transferrable sheet can be positively transferred and which exhibits superior running performance and resistance to blocking to enable a picture of high quality and high resolution to be produced.
The present invention provides a receiver paper made up of a substrate and a dye reception layer formed thereon, wherein the dye reception layer contains a copolymer of a compound having the following formula (1): 
wherein R is H or CH3, with another monomer, and wherein the proportion in the copolymer of the compound having the formula (1) ranges from 5 to 25 wt %.
With the above-described receiver paper according to the present invention, in which a copolymer of the compound shown by the chemical formula (1) and an acrylic resin is used as a material for the receiver paper, and in which the proportion in the copolymer of the compound shown by the chemical formula (1) is prescribed to a pre-set range, the dye reception layer can be set to a desired state of flexibility. Specifically, the proportion of the compound having the chemical formula (1) is set to 5 to 25 wt %. If the proportion of the compound having the chemical formula (1) is set to less than 5 wt %, the dye reception layer is lowered in strength, whereas, if the proportion of the compound having the chemical formula (1) is set to larger than 25 wt %, the glass transition temperature of the copolymer becomes low to soften the dye reception layer excessively.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.